锡系固体超强酸在氧化反应中的研究

【作者】 崔雪；

【导师】 王博；

【作者基本信息】 陕西师范大学 ， 化学工艺， 2008， 硕士

【摘要】 固体超强酸SO₄^2-／SnO₂（酸强度H₀<-16）已经广泛的应用于催化烷烃的异构化反应、酯化反应、氧化反应、芳构化、聚合反应等等，并显示出良好的催化活性。被认为是当今酸催化领域重要的催化剂，引起国内外研究者广泛关注。传统的催化剂一般使用Lewis酸（AlCl₃，FeCl₃等）和质子酸（HF），但这些催化剂存在许多弊端，如选择性较差、副反应多、收率低、催化剂无法回收、腐蚀性强、产物分离困难、环境污染严重等。而固体超强酸符合绿色催化的要求，具有广泛的应用前景。在现代化工行业中以空气为氧化剂辅以催化剂催化氧化碳氢化合物有着重大的经济效益。本文对固体超强酸的发展及种类进行了综述。并简单介绍了烷烃氧化的研究现况。基于固体超强酸自身特点和烷烃的氧化研究的基础上提出了本课题的研究内容：以锡系固体超强酸SO₄^2-／SnO₂和金属改性锡系固体超强酸SO₄^2-／SnO₂-M_XO_Y（M=Ce，Co，V，Mo，Ti）为催化剂，以空气中的氧气为氧化剂，在温和的实验条件下将正庚烷直接催化氧化生成聚合物、酯、芳烃化合物等。本论文的研究主要包括以下几个方面：（1）SO₄^2-／SnO₂和SO₄^2-／SnO₂-M_XO_Y（M=Ce，Co，V，Mo，Ti）固体超强酸由共沉淀法制备，并利用SEM、XRD、BET、FT-IR和XPS等手段对催化剂进行了表征；（2）通过催化氧化正庚烷反应考察催化剂SO₄^2-／SnO₂的活性。整个反应过程产物由GC-MS进行跟踪测定。在隔绝空气的条件下，主要产物为聚合的直链烷烃（碳链长度在14-22之间）；在空气的氛围下，产物中又出现了含氧产物，例如：2-异丙基-环己醇、异丁基邻苯二甲酸酯和甲基环己烷基十三烷基草酸酯，可以应用于燃料、皮革、纺织品、化妆品等行业。这一在常温常压下以锡系超强酸为催化剂催化氧化碳氢化合物的反应还未见报道：（3）金属改性锡系固体超强酸SO₄^2-／SnO₂-M_XO_Y（M=Ce，Co，V，Mo，Ti）在催化氧化反应中表现出很好的催化活性，通过研究表明金属改性剂的加入提高了催化剂酸性，选择性和稳定性；（4）具有光催化活性金属Ti的引入极大的提高了催化剂SO₄^2-／SnO₂的比表面积。并且在紫外光的照射下催化剂SO₄^2-／SnO₂-TiO₂在氧化正庚烷的反应中表现出了良好的光催化活性。开启了固体超强酸应用的一个新的领域；（5）最后一部分简单介绍了可能的反应机理。相对于其它传统的催化氧化碳氢化合物的生产工艺，SO₄^2-／SnO₂-M_XO_Y在空气氛围下催化氧化这种方法的优点在于：操作简单、反应条件温和，反应时间短等等。通过这种方直接氧化有机物有望应用在烷烃氧化实际生产中。更多还原

【Abstract】 Solid superacid SO₄^2-/SnO₂ （H₀ < -16） has been used in isomerization, alkylation, acylation, polymerization, oligomerization, esterification, oxidation, etc. It can be said that solid acids are the most important heterogeneous catalysts used today. The conventional catalysts are Lewis acid （AlCl₃, FeCl₃, TiCl₄, BF₃, etc） and proton acid （HF, H₂SO₄, HCl）, but these catalysts have many disadvantages, such as bad selectivity, more side reaction, low yield, strong corrosion, difficulty in separation and recovery, serious environmental pollution etc. Solid acids are green industrial catalyst that is helpful to recycling and possesses wide prospect of application. Catalytic oxidations of hydrocarbons using oxygen or air as oxidants are significant and economical to the chemical industry.In this article, the basic knowledge of development and species of the solid superacid (especially SO₄^2-/SnO₂) and oxygenation of alkanes is introduced and reviewed. The content of this subject study is presented on the basis of studies on solid superacid and oxygenation of alkanes. The direct oxidation of n-heptane to ester using air as the oxidant under mild conditions assisted by solid superacid SO₄^2-/SnO₂ and metal-promoted sulfated tin oxide catalysts SO₄^2-/SnO₂-M_XO_Y （M= Ce, Co, V, Mo, Ti）. The major aspects of the present study are as follows:（1） In the first part of this article, catalyst prepared by chemical co-precipitation method and characterized by means of SEM, XRD, BET, FT-IR and XPS techniques was studied.（2） Catalytic SO₄^2-/SnO₂ activity was tested for the directly oxidation of n-heptane. Products were analyzed with an on-line gas chromatograph-mass spectrometry. Under airtight conditions, main products are C-number of n-alkane from C₁₄ to C₂₂; under aeration conditions, oxygenate compounds presented. Some products such as: diisobutyl phthalate, cyclohexylmethyl tridecyl oxalate and 2-isopropylcyclohexanol that have not been reported in the directly oxidation of alkane by traditional method have been obtained, and all the products are used in fuel, leather, textiles, cosmetics and so on.（3） Metal-promoted superacids SO₄^2-/SnO₂-M_XO_Y （M= Ce, Co, V, Mo, Ti）, which were highly active for this reactions, were investigated in order to improve its acid sites activity, selectivity and stability.（4） The introduction of Ti into SO_<sup>2-/SnO₂ can increase its surface area greatly. SO₄^2-/SnO₂-TiO₂ shows a certain photocatalytic activities in n-heptane oxidation using air as the oxidant in the presence of UV light. This new application of solid superacid also sets light on its special characteristics and its application field.（5） Finally, the article discussed the possible mechanism of these reactions.Compared with catalytic oxidations of hydrocarbons by traditional methods, simple work up procedure, milder reaction conditions, and shorter reaction times are the advantages associated with the SO₄^2-/SnO₂-M_XO_Y catalyzed processes. The present study revealed that SO₄^2-//SnO₂/M_XO_Y as a heterogeneous catalysis might hold great promise in the development of oxygenation of alkanes.更多还原